Evolution of Phosphorus Concentration in Surface Runoff from Pastures Fertilized with Broiler Litter

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Previous research has shown that surface application of broiler litter to pastures can lead to elevated concentrations of dissolved reactive phosphorus (DRP) in surface runoff. It is not clear, however, for how long a after broiler litter application DRP concentrations in runoff remain high. This work was conducted to study the evolution of DRP concentration in surface runoff from pastures that received broiler litter in 1995 and 1996, and only inorganic fertilizer Nin 1997 and 1998. The results showed that DRP concentrations in surface runoff remained high (> 2 mg P L-1) while broiler litter was being applied. Once broiler litter applications stopped, DRP concentrations in runoff decreased below 1 mg p L-1 within 19 months. These results suggest that the risk of contaminating surface waters with DRP could be decreased by fertilizing pastures with broiler litter every two or three years, with the addition of only fertilizer N in those years when broiler litter is not applied.